Traditional surgical lighting systems include at least one but usually two or more incandescent lamps disposed in large ceiling supported luminaries. The incandescent bulbs generate large quantities of good quality light. Generally, a color rendering index (CRI) is used as a relative measure of how well an object will be recognized under the light. The incandescents have a good CRI. The need for a high color rendering index is especially acute during surgical procedures because the look and color of the illuminated tissue often provides surgeons with critical visual feedback information. Over the years, complicated reflector and lensing arrangements have been implemented in the lightheads to provide for shadowless illumination of the surgical site and to enable easy manual adjustment of beam spot size for further enhancing the capabilities of the traditional lighting systems.
Although these prior systems have been somewhat successful in addressing the basic needs of surgeons and are relatively inexpensive, the incandescent lamps or bulbs used impose a serious fundamental performance limitation. More particularly, lighting systems that use incandescent bulbs are notorious for having poor efficiency and short life. They also generate a substantial amount of radiation in the infra-red range. This causes undesirable heat that can potentially damage the tissue below the lighthead.
In commercial and industrial applications, metal halide lamps have been proposed as a substitute for traditional incandescent bulbs because they offer an improved energy efficiency, longer life, and better light to heat ratio. In that technology, a pair of spaced apart electrodes extend into a pressurized chamber that holds liquid/gaseous halide material. An external power source is connected to the pair of spaced apart electrodes to supply a large voltage across the free ends of the electrodes within the chamber. The high voltage causes the halide material mixture to ionize, thereby allowing a small current to pass therethrough. For as long as the current is sustained, a light-emitting plasma discharge is generated within the lamp.
Although metal halide gas discharge lamps typically have the above advantages over incandescent lamps, they have a generally low CRI and sometimes suffer from inadequate color stability and poor lamp-to-lamp color variability. In order to achieve desired performance characteristics, very small amounts of selected caustic compositions are required. The dosing is hard to control and the chemicals often cause seal failure in the lamp and accelerated electrode corrosion.
Color stability is adversely affected in metal halide discharge lamps whenever they are moved during use. This is because as the energized bulbs are subjected to motion, the liquid halide mixture pool within the bulb flows to regions of different temperatures causing the composition of the liquid/gaseous mixture to change. The mounted within the reflector of a ceiling supported luminaire for use in a surgical lighting system. The teachings of that patent are incorporated herein by reference.
Two significant problems with systems that use electrodeless metal halide discharge lamps in conventional lightheads, such as described in the ""706 patent, however, are the orientation sensitivity and partial blockage of the light by the electric field coils used to couple electric energy to the liquid/gaseous mixture. Shadow control and field coil physical size requirements become a limiting factor as well. In addition, the bulb generates heat within the lighthead itself which in turn could cause some discomfort to the surgical staff. Large cooling fins are required on the back side of the lighthead to dissipate heat so that the reflector portion is not hot to the touch.
Accordingly, it would be desirable to use the high quality light energy produced from metal halide lamp technology, particularly electrodeless metal halide lamps, in medical and surgical applications. It would be further desirable to utilize light from a metal halide lamp source in surgical applications but without physically locating the lamp within the lighthead. It would therefore be desirable to locate a metal halide light source at a remote area and then port the light through a large collection of fiber optic cables so that the light is conducted/distributed to one or more distant end users.
A preferred embodiment of the present invention consists of an electrodeless metal halide lamp coupled in combination with a plurality of fiber optic cables to distribute and deliver light to one or more remote locations, preferably operating rooms, examination rooms, sloshing liquid also adversely affects the corrosion resistance of the electrodes.
Lastly, as noted above, metal halide discharge lamps have an overall poor lamp-to-lamp color variability. In general, the gaseous/liquid mixture contained within the bulb requires very small amounts of critical materials, the proportion of which relative to the overall mixture is hard to control. Therefore, typically, each metal halide discharge lamp has a unique and often very different color spectrum.
In view of the above drawbacks, metal halide discharge lamps have met with little success in surgical lighting systems. The physical size of the bulbs and the heat generated during their operation make it impractical to place metal halide lamps within medical lightheads. Only one known commercial offering, the Martin ML 702 product, uses a metal halide discharge lamp in a conventional surgical luminaire.
Electrodeless metal halide (EMH) lamp technology offers improved performance relative to the above-described standard incandescent and metal halide discharge lamps. These lamps, as their name implies, have no electrodes but, rather, rely on electromagnetic high frequency (radio frequency) power to generate and sustain the light emitting plasma discharge within a lamp capsule. A pair of high frequency coils are disposed on opposite sides of a sealed capsule containing a liquid/gaseous halide mixture. Since the coils are disposed on the outside of the capsule, they are out of physical contact with the halide mixture. This construction directly enables a wider range of chemistry to be used within the bulb and, in turn, leads to the ability to achieve higher life cycles, and higher color rendering index (CRI).
U.S. Pat. No. 5,861,706 describes an electrodeless high intensity discharge lamp physically fixtures within one or more rooms, outlets within one or more rooms, and to centralized light devices within one or more rooms. The light from the fiber optic cables is usable to power, in one or more selected combinations, ambient room lighting, major surgical luminaires, minor examination lights, various light appliances such as surgical head lights, endoscopes, or any other use for medical applications.
Preferably, the light source is an electrodeless metal halide (EMH) discharge lamp arranged in a suitable remote lighting center. A plurality of flexible fiber optic cables are used to communicate and distribute the light energy from the lighting center source to a plurality of lighting fixtures, utility drop points, and other xe2x80x9clight consumingxe2x80x9d apparatus. The preferred EMH lamp has sufficient power to enable multiple light users to simultaneously access the light through the fiber optic cable bundle at locations remote from the lighting center. For example, the light can be supplied from a distance to multiple rooms or to multiple locations within a hospital.
One aspect of the present invention is that an electrodeless metal halide light source is used within the lighting center, which is in turn remotely disposed relative to the end users. Preferably, the lighting center is positioned far from sterile areas and at a location that helps facilitate regular maintenance and, as a preferred example, in the ceiling or wall. High efficiency fiber optic cables are used as conduits to port the light through ceilings, walls, and various fixture support mechanisms to multiple points of use.